CPS Core Performance

Test Environment

TO DO Laptop specs

The performance tests are written in Groovy (a JVM language). As all CPS Core operations are synchronous, the results here are to be considered as single-threaded operation only.

Test data

Test data used complies with Open ROADM YANG model - a real-world model for optical devices. Specifically, openroadm-device nodes consisting of 86 fragments are created. For example, a test that creates 1000 device nodes will result in 86,000 fragments in the database. Some tests use up to 3000 device nodes (258,000 fragments - equivalent to around 20,000 CM-handles in NCMP), with four anchors replicating the data, meaning that the system has been tested up to 1 million fragments.

Storing data nodes

A varying number of Open ROADM device nodes will be stored using CpsDataService::saveData.

Observations

• Storing data nodes has linear time complexity (as expected).
• Raw performance is roughly 3000 fragments per second for the given test setup.
• Performance can be improved by enabling write batching (CPS-1795)
• There are edge cases with exponential complexity (adding books to the bookstore model).

Commentary

The current database schema does not allow for Hibernate to use JDBC write batching. There is work in progress to address this.

JPA/Hibernate is not well-suited to tree-structured data. As an example, writing data nodes / fragments happens in two low-level steps:

• SQL INSERT to create the fragments
• SQL UPDATE to set the parent IDs of those created fragments
• meaning each created fragment requires two DB operations

There is work in progress to address this behavior using a custom algorithm using JDBC. The use of a graph database would implicitly fix such issues.

Updating data nodes

In this scenario, 1000 Open ROADM device nodes are already defined. A number of these existing data nodes will be updated using CpsDataService::updateDataNodeAndDescendants.

Observations

• Updating data nodes has linear time complexity (as expected).
• Raw performance is roughly 600 fragments per second for the given model and test setup.
• Updating data nodes is 5 times slower than storing data nodes.

Commentary

This is the weak spot of all write operations. It could be as fast to simply delete and recreate the data.

A custom algorithm comparing existing data against updated data (delta algorithm) may be required to improve performance here. This could also indicate that Hibernate is not being used effectively.

Updating data leaves

In this scenario, 1000 Open ROADM device nodes are already defined. The data leaves of a number of these existing data nodes will be updated using CpsDataService::updateNodeLeaves.

Example JSON payload for updating data leaves for one device:

{
    'openroadm-device': [
        {'device-id':'C201-7-1A-1', 'status':'fail', 'ne-state':'jeopardy'}
    ]
}

Test Results

Observations

• Updating data leaves has linear time complexity.
• Raw performance is about 3000 fragments per second.
• This is very fast compared to updating whole data nodes. I recommend that NCMP use this API for updating CM-handle state.

Commentary

The performance of this function is excellent, and yet it may be improved by write batching.

Deleting data nodes

In this scenario, 300 Open ROADM device nodes are already defined. A number of these data nodes will be deleted using CpsDataService::deleteDataNodes. The types of nodes will be varied, for example, deleting container nodes, list elements, or whole lists.

Test results

Observations

• Delete performance is linear on the amount of data being deleted (as expected).
• Raw performance of deleting container nodes is around 40,000 fragments per second. (So we can delete data nodes around 10x faster than creating them.)
• Deleting lists is much slower than deleting the parent container of the list (which can be easily improved).
• Of note, attempting to delete non-existing data nodes takes longer than actually deleting the equivalent amount of nodes with descendants - it is a slow operation.

Suggested improvement: For whole list deletion, add a condition to the WHERE clause in the SQL for deleting lists, to narrow the search space to children of the parent. For example:

SELECT * FROM fragment WHERE (existing conditions)

  AND parent_id = (SELECT id FROM fragment WHERE xpath = '/parent-xpath')

This should narrow the performance gap in this case.

Reading data nodes

In these tests, a varying number of Open ROADM devices are created and retrieved.

Reading top-level container node

In this test, CpsDataService::getDataNodes is used to retrieve the top-level container node.

Test results

Reading the top-level container node with no descendants:

The above data clearly indicates constant time.

Reading the top-level container node with all descendants:

Observations

• Reading a single top-level container node with no descendants has constant time (as expected).
• Reading a single top-level container node with all descendants has linear time (as expected).
• Raw performance of reading with all descendants is roughly 100,000 fragments per second.

Commentary

This is the fastest operation in CPS, in terms of fragments per second. This is not surprising, as a simple read should be the fastest operation.

Reading data nodes for multiple xpaths

This test uses CpsDataService::getDataNodesForMultipleXpaths with all descendants to retrieve a varying number of Open ROADM device nodes.

Test results

Special case: attempting to read multiple non-existing data nodes

In this case, we attempt to read many non-existing data nodes:

The above case appears to be constant time, but theoretically must be linear - we'll call it negligible time.

Observations

• Reading many data nodes with all descendants has linear time (as expected).
• Attempting to read many non-existing data nodes takes negligible time.
• Raw performance of reading many with all descendants is roughly 80,000 fragments per second.

Additional test cases: Reading container node versus list

Recently, functionality was added to enable reading whole lists (CPS-1696). Here we compare performance of reading a container node containing a list, versus reading the list (with all descendants).

As can be seen, it is slower reading the list than reading the parent node containing the list.

Suggested improvement: Add a condition to the WHERE clause in the SQL for reading lists, to narrow the search space to children of the parent. For example:

SELECT * FROM fragment WHERE (existing conditions)

  AND parent_id = (SELECT id FROM fragment WHERE xpath = '/parent-xpath')

This should narrow the performance gap in this case.

Cps Path Queries

TO DO

There have been massive orders-of-magnitude improvements to query performance. Formerly, queries had quadratic complexity, which is now linear. In the last month alone, performance has improved by 100x.

See here for a previous PoC analysis: CPS-1646 CpsPath queries using path-component lookup

Comparison of NCMP Performance across versions

CM-handle registration

CM-handle registration is multi-threaded, so performance may appear to scale better than linear, until the CPU cores are maxed out.

As can be seen below, CPU usage never reached 100% during the tests of the current version.

CM-handle de-registration

Current release has exactly linear performance for CM-handle de-registration (on a single thread):

Commentary

CM-handle de-registration is a synchronous operation. Since the above tests send a single large batch, the operation is performed in a single thread. The linear performance reflects this. If the operation was broken into many smaller requests, the expectation is that it would complete many times faster - but this has not been tested.